A virtual package is a technology aimed to expand the content of a read-only recording medium, by constructing a virtual package by dynamically combining data recorded on a read-only recording medium such as BD-ROM, with data recorded on a rewritable recording medium such as a hard disk. In such technologies, data recorded on a rewritable hard disk is updated, so that a work recorded on a BD-ROM can be changed even after the BD-ROM is distributed. For example, a provider of movie works can provide a digital stream of previews of the latest movies via a network, even after having distributed BD-ROMs on which the main part of a movie is stored. This makes it possible to advertise the latest movies to the users regardless of the timing of the distribution of the BD-ROMs.
The following Patent Documents 1, 2, and 3 describe conventional technologies related to a virtual package.                Patent Document 1: Japanese Patent Application Publication No. 2006-109494        Patent Document 2: Japanese Patent Application Publication No. 2007-20211        Patent Document 3: Japanese Patent Application Publication No. 2006-33067        